1. Field of the Invention
This invention relates to a sterilization container for use in sterilizing, storing and transporting and presenting instruments, in particular medical instruments.
2. Background of the Invention
Most, reusable medical instruments require sterilization before each use. Many methods are employed for sterilization, but the most prevalent methods include: steam autoclaving, vapor phase chemical sterilization and vapor phase chemical sterilization in combination with a plasma field. The chemical sterilants include hydrogen peroxide and ethylene oxide. One of the most versatile, quickest and most effective methods employs an initial period of vapor phase hydrogen peroxide followed by application of an electromagnetic field which drives the hydrogen peroxide vapor into the plasma state of matter. The plasma phase enhances the sterilization and when the electromagnetic field is released the plasma free radicals recombine to form water and oxygen.
Typically, instruments are placed into a container and then the container is placed into the sterilization device. Portals for the passage of sterilizing media must be provided. Also, the container is usually provided with a filter material which allows passage of the sterilizing media through the portals and container yet prevents the ingress of microorganisms. The portal and filter material may be combined as in the Nichols U.S. Pat. No. 4,704,254, issued Nov. 3, 1987 and incorporated herein by reference, or the container may be provided with a plurality of apertures and then be wrapped prior to each sterilization in a filter wrapping material such as SPUNGUARD brand CSR wrap available from Kimberly Clark Corporation which is a spunbonded/meltblown/spunbonded (SMS) laminate consisting of nonwoven outer layers of spun-bonded polyolefins and an interior barrier layer of melt-blown polyolefins.
Usually, holding devices of one form or another hold one or more individual instruments within the container. The holding device may comprise clips or other such arrangements, which may or may not be specially adapted to hold a particular medical instrument. One popular holding device simply comprises a plurality of upwardly extending flexible projections, sometimes called fingers, which prevent the instruments from moving about within the container and provide minimal contact with the instruments. Typically, these are provided on a mat which lies in the bottom of the container.
The ideal sterilization tray or container is compatible with all major sterilization methodologies, minimizes or eliminates condensation collection through thin, yet strong, walls, has a long life, is easy to operate and can be provided for a reasonable cost. Containers presently known suffer from shortcomings which limit their performance in one or more of these areas. For instance, many trays designed for steam autoclaves are formed of stainless steel which may interfere with formation of a plasma in some systems. Other trays made of polymers may not have sufficient heat resistance to withstand repeated steam sterilization cycles. Some tray materials interact with chemical sterilants, and may even decompose the sterilant. Other materials may absorb excessive amounts of chemical sterilants, thereby decreasing the sterilization effectiveness by decreasing the amount of sterilant available for sterilizing.
A sterilization container system for sterilizing instruments according to the present invention allows multiple sterilization enclosures to be stacked vertically during a sterilization procedure while maintaining adequate diffusion of sterilant into the enclosures. The system comprises a first enclosure having a bottom surface and an upstanding sidewall therefrom and a second enclosure having a bottom surface and an upstanding sidewall therefrom. A stacking device fits between the first enclosure and the second enclosure, the first enclosure being disposed above the second enclosure. The stacking device comprises one or more spacers between the first enclosure and the second enclosure to elevate the first enclosure above the second enclosure and side members connected to the one or more spacers and disposed lateral of the first enclosure and second enclosure whereby to inhibit lateral movement of the first enclosure with respect to the second enclosure thus providing a flow path through the stacking device and between the first enclosure and the second enclosure.
Preferably, an interior of the second enclosure is in fluid communication with an environment surrounding through the flow path through the stacking device. For instance, the second enclosure can comprise a top surface connected to the first enclosure upstanding sidewall, this top surface having one or more diffusion apertures therethrough. The first enclosure bottom surface preferably comprises one or more diffusion apertures therethrough. Preferably, the side members comprise a wall having an elongated lateral opening. Preferably, the elongated lateral openings have a height which matches the spacing between the first enclosure and the second enclosure. In one preferred embodiment, the stacking device has a rectangular shape with one of the spacers in each corner.
Preferably, the first enclosure, the second enclosure and the stacking device are formed of a thermoplastic liquid crystal polymer and resist chemical attack from hydrogen peroxide, and ethylene oxide, resist absorption by hydrogen peroxide, do not unduly interfere with any electromagnetic fields, and resist attack from elevated temperatures of steam sterilization. The thermoplastic liquid crystal polymer preferably comprises a wholly aromatic polyester. Suitable examples include: polybenzoate-naphthalate; polybenzoate-terephalate-bisphenol-isophthalate; polybenzoate-terephalate-ethylene glycol; and polynapthalate-amino terephthalate.
The container system can comprises more than two enclosures and more than one stacking device. In one preferred embodiment, the stacking device comprises outwardly facing ribs on the side members whereby to stiffen the stacking device and separate it horizontally from an another adjacent stacking device. Each of the enclosures can further includes means for holding a medical instrument against movement within the container. Preferably, ingress to each of the enclosures is filtered through a filter permeable to sterilizing vapors and impermeable to contaminating microorganisms, such as by the filter being wrapped about each of the enclosures.
A method of sterilizing instruments according to the present invention comprising the steps of: placing one or more of the instruments into a first enclosure; placing one or more of the instruments into a second enclosure; stacking the first enclosure atop the second enclosure with a stacking device between the first enclosure and the second enclosure, the stacking device vertically separating the first enclosure and the second enclosure and restraining horizontal movement of the first enclosure with respect to the second enclosure; and diffusing a sterilant between the first enclosure and the second enclosure and into the second enclosure through an upper portion thereof.